Central telephone exchange offices utilize DC power to run various telephone communication equipment. DC power is brought into the office to a main switch (or power supply) board from where it is directed to various equipment by power cables. The separation between the main switch board and the power cables is provided typically by DC circuit breakers intended to shut down the equipment in case of short circuits.
Very often an arcing arises between conductors in the cable which if undetected leads to a fire first hidden inside the cable cover and subsequently to an observable fire consuming the cable. Arc discharges within a cable may arise due to a number of factors one of which could be a fault in the insulation on separate conductors in a multiconductor cable. Such a fault could be a result of a manufacturing flaw or damage to the conductor within the cable. Such damage may occur in the course of transportation, installation or use of the cable. Stepping on, kicking or some other damaging act to the cable either during the installation or use in the office may be a contributory cause of the injury.
Arc discharges which may begin as an occasional sparking between adjoining conductors within the cable, if undetected, may lead to a fire within the cable. Arc discharges occur at relatively low current levels of from 0.5 to 10 amperes. However, a typical central office circuit breaker operates at 40-50 ampere level. Thus, the circuit breakers do not recognize such arc discharges permitting the arc discharges to continue with resultant overheating of the cable leading to a fire of the cable and consequently in the central office.
It is desirable to timely detect occurrence of arc discharges in DC power cable and to shut down the equipment prior to occurrence of such arc discharges which could lead to cable fires.